Each CSA member has a cash account for de minimis refunds and monies due your farmer. If the balance due, see your Member Dashboard, is positive this amount can be used by you for future purchases/billings. You will see this amount applied on an order. If the cash account balance is negative--in red--this is what you owe the farmer. This can be paid immediately from your member dashboard.
Member cash accounts are also used to manage over/under box values for customized shares. Most farms have a minimum amount for auto-billing of a credit card, so you may carry a small balance due until you reach that minimum.
Other uses for the cash account are to refund member for spoiled or undelivered product (like broken eggs); and conversely to show an amount due for delivery of unpaid-for product.